Proteolytic enzyme activities have been identified in rat and calf lens soluble protein fractions: neutral proteinase, leucine amino-peptidase and arylamidase. Using calf lens and normal and cataractous rat lenses, the neutral proteinase will be further purified and characterized, and the products of both endogenous and artificial substrates will be studied. The calf lens alpha1-crystallin fraction, which contains the neutral proteinase, has been shown to contain the same proportion of alpha A and alpha B subunits present in alpha-crystallin. The alpha 2-crystallin, an endogenous substrate used to assay neutral proteinase activity, also contains alpha A and alpha B subunits in the same proportion as alpha-crystallin. To determine the relative susceptibility of lens proteins to hydrolysis by the neutral proteinase, the two basic and the two acidic subunits of alpha-radioisotope and tested as substrates. Products of these enzyme hydrolyses will be examined by chromatographic analysis and autoradiography. Radioiosotope labelled low molecular weight proteins of known amino acid sequence will be used to determine peptide bond specificity of the enzyme. A detailed knowledge of the specificity substrates, and products of the neutral proteinase will be instrumental in determining the in vivo role of the enzyme in normal lens development and cataractogenesis.